Coating composition and uses thereof

ABSTRACT

A coating composition comprising a photocatalyst composite and a silicone resin is provided, in which the content of the photocatalyst composite ranges from about 1% to about 70% by weight (wt %), based on the total weight of the coating composition, and the photocatalyst composite contains a heat insulation material and a photocatalyst material. An energy-saving material is further provided, which includes a substrate and a film formed from the coating composition of the present invention on at least one of the surfaces of the substrate. The energy-saving material is capable of effectively shielding off infrared (IR) light, substantially decreasing indoor temperature, and reducing power consumption. In addition, in the presence of the photocatalyst which can absorb ultraviolet light, the material also exhibits good superhydrophilic and self-cleaning properties and provides antimicrobial and deodorization effects.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a coating composition, which can becoated on a substrate, so as to enable the surface of the substrate tohave self-cleaning and heat insulation effects. The present inventionfurther relates to an energy-saving material containing a film formedfrom the coating composition of the present invention.

2. Description of the Prior Art

There are many materials for shielding the heat effect of infrared lightavailable in the market, for example, glass curtain of a building,automobile glass, and heat insulation paper. In short, the materials areprovided for the purpose of allowing the sunlight to pass through toprovide light, while the heat source (that is, heat effect of infraredlight) is expected to be insulated. However, with an existing glasshaving the infrared light shielding property as an example, theproduction cost is too high and the effect is less satisfactory. Forexample, it is known that an ultra thin infrared light absorption silverfilm may be embedded in the glass to shield the infrared light; however,the preparation cost is high, and silver is easily oxidized, and thusloses the infrared light shielding effect.

In addition, a material (for example, titanium dioxide of highrefractive index and silica of low refractive index) capable ofshielding the infrared light may be applied on glass or a lens by vacuumevaporation, to form a film capable of shielding the infrared light.However, the film thus formed has the following disadvantages of highcost, complex manufacturing process, and unsatisfactory effect, thus notmeeting the requirement of economic benefits.

In addition to the above two methods, an alternative low-cost solutionis proposed, in which a pigment or a dye is admixed in the glass toabsorb the infrared light in sunlight. However, upon irradiation withintense sunlight or scattered light, a fume like haze occurs to thiskind of glass containing pigment or dye, and thus the infrared lightabsorbing performance is influenced, and the pigment or dye will bedecomposed after long time of use and lose the corresponding effects.

Furthermore, it is known that the photocatalyst has a function ofabsorbing light (especially, UV light) to excite the electrons, and thushas a photocatalytic performance. After excitation with light, thephotocatalyst material activates water molecules or oxygen molecules inthe air, to form hydroxyl radicals or negative oxygen ions for oxidationreduction reaction, so as to decompose pollutants in the environment.Thereby, the photocatalyst material may be used to remove the pollutantsin the air or waste water, and inhibit bacteria attached to a surface,so as to achieve an antimicrobial effect. Furthermore, upon irradiationwith light, free radicals or negative oxygen ions are formed andreleased from the surface of the photocatalyst material due to thepresence of hydrogen molecules, and an empty position is formed at theposition originally occupied by oxygen. In this case, if any, the watermolecules in the environment will occupy the empty position and lose aproton, to form a hydroxyl group, such that the photocatalyst materialexhibits a superhydrophilic property, thereby achieving theself-cleaning and anti-fog effect.

Generally, as for a heat insulation film or window glass coating havingthe infrared light shielding and UV light absorbing functions,multi-layer processing is required to be performed on a substrate, toform a composite film, the preparation process is complex, and thepreparation cost is high. Therefore, continuous efforts are currentlydirected to provide a material having infrared light shielding and UVlight absorbing functions.

SUMMARY OF THE INVENTION

In order to achieve the above objectives, the present invention providesa coating composition comprising a photocatalyst composite and asilicone resin, in which the content of the photocatalyst composite isabout 1 to 70% by weight (wt %), based on the total weight of thecomposition, and the photocatalyst composite comprises:

(1) a heat insulation material, selected from the group consisting ofantimony tin oxide (ATO), indium tin oxide (ITO), aluminum zinc oxide(AZO), indium zinc oxide (IZO), and gallium zinc oxide (GZO), and acombination thereof; and

(2) a photocatalyst material, selected from the group consisting oftitanium dioxide, zinc oxide, strontium titanate, and tin oxide, and acombination thereof, wherein the content of the photocatalyst materialis about 10 to 90 wt %, based on the total weight of the photocatalystcomposite.

The present invention further provides an energy-saving material, whichincludes a substrate and a film applied on at least one of the surfacesof the substrate, in which the film is formed from the coatingcomposition of the present invention, and has self-cleaning and heatinsulation effects.

The coating composition of the present invention can effectivelyinsulate or reflect the heat-causing infrared light, such that thetransmittance of the infrared light is greatly reduced. Thephotocatalyst material exhibits an UV light absorbing capability, aself-cleaning function, and anti-fog, antimicrobial, and deodorizationeffects. Furthermore, the coating composition of the present inventionmay be applied on a substrate through a common coating method, and thusthe preparation process is relatively simple and cheap.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a comparison chart of light transmittance according to Example1.

FIG. 2 shows the decomposition rate of the coating composition of thepresent invention for methylene blue, which indicates the photocatalyticproperty of that the coating composition.

FIG. 3 shows measurement values of a contact angle of the coatingcomposition of the present invention and water upon irradiation with UVlight.

DETAILED DESCRIPTION OF THE INVENTION

The term “about” used herein means a variation of ±10% of an indicatedvalue.

The coating composition of the present invention comprises aphotocatalyst composite and a silicone resin, in which the content ofthe photocatalyst composite is about 1% to about 70 wt %, and preferablyabout 40% to about 60 wt %, based on the total weight of thecomposition. If the content of the photocatalyst composite is lower than1 wt %, the infrared light shielding and UV light absorbing effects ofthe composition is insufficient; and if the content is higher than about70 wt %, the dispersivity of the photocatalyst composite in the resin issharply decreased, and the coated composition is likely to fall off.

The photocatalyst composite comprises a heat insulation material and aphotocatalyst material, in which the content of the photocatalystmaterial is about 10% to about 90 wt %, and preferably about 40% toabout 85 wt %, based on the total weight of the photocatalyst composite.

The photocatalyst composite normally has a particle size of from about 2to about 100 nanometers (nm), preferably from about 5 to about 45 nm,and more preferably 10 to 35 nm. If the particle size is smaller than 2nm, the photocatalyst composite is not easy to produce and is notpractical, and if the particle size is greater than 100 nm, the overallsurface area becomes small, and thus the transmittance of the visiblelight decreases, and the heat insulation effect is poor. As the particlesize of the photocatalyst composite of the present invention is smallerthan the wavelength of visible light (from about 380 nm to about 780nm), when the photocatalyst composite is irradiated with light, thetransmitted light will not be seriously scattered, thereby avoiding theadverse influence on the quality of the transmitted light.

The heat insulation material in the photocatalyst composite of thepresent invention is required to have an infrared reflectivity of about70% or higher, and can be selected from the group consisting of antimonytin oxide (ATO), indium tin oxide (ITO), aluminum zinc oxide (AZO),indium zinc oxide (IZO), and gallium zinc oxide (GZO), and a combinationthereof.

According to a preferred embodiment of the present invention, when usingITO or ATO as the heat insulation material of the photocatalystcomposite, substantially a same heat insulation effect can be achievedat a less material dose, as compared with other materials, thus thephotocatalyst composite is more cost effective. Moreover, it is foundthat when the coating composition includes ITO, it not only caneffectively reflect infrared light but exhibits a better visible lighttransmittance and can be advantageously used as a transparent heatinsulation material.

According to a preferred embodiment of the present invention, preferredtransparency can be achieved when ITO is used as the heat insulationmaterial of the photocatalyst composite. In addition, it is found thatwhen using ITO in the coating composition of the present invention, theinfrared light can be effectively reflected, and substantially a sameheat insulation effect can be achieved at a less material dose, comparedwith other materials, thus being more cost effective.

In addition to the heat insulation material capable of shielding off orreflecting IR light, the photocatalyst composite in the coatingcomposition of the present invention further comprises a photocatalystmaterial. The photocatalyst material has a function of absorbing UVlight to excite electrons, and thus has photocatalytic property. Uponexcitation with light, the photocatalyst material activates watermolecules or oxygen molecules in the air to form hydroxyl free radicalsor negative oxygen ions for oxidation reduction reaction, so as todecompose pollutants in the environment. Therefore, the photocatalystmaterial may be used to remove the pollutants in the air or waste water,and inhibit bacteria attached to a surface so as to achieve anantimicrobial effect. Furthermore, the photocatalyst material alsoexhibits a superhydrophilic property, and the moisture may form into anaqueous film between the fouling and the photocatalyst material, suchthat the adhesion of the fouling is reduced, and the fouling on theaqueous film can be easily removed after being washed with water orrainwater. Thus, the photocatalyst material has a UV light absorbingcapability and a self-cleaning function, and provides anti-fog,antimicrobial, and deodorization effects.

The photocatalyst material suitable for the photocatalyst composite ofthe present invention can be any of those well known to persons skilledin the art, and may be, for example, titanium dioxide, zinc oxide,strontium titanate (SrTiO₃), tin oxide, or a mixture thereof, and ispreferably titanium dioxide which is relatively harmless to theenvironment or human body. In terms of catalyst performance, titaniumdioxide in an anatase crystal structure is preferred. Furthermore, theparticle size of the photocatalyst material is required to be smallerthan about 100 nm, so as to exhibit a photocatalytic effect. Forexample, the particle size of titanium dioxide is suitably about 1 toabout 100 nm, and preferably about 5 to about 30 nm; if the particlesize is less than 1 nm, titanium dioxide is difficult to be produced andnot easy to be dispersed, and if the particle size is greater than 100nm, the photocatalytic effect will be greatly decreased.

The coating composition of the present invention comprises a binderwhich can be, for example, but is not limited to an acrylic resin,fluorocarbon resin or silicone resin. To prevent the photocatalyst frombeing oxidized and being decomposed, the binder is preferably a siliconeresin. The silicone resin contained in the coating composition of thepresent invention is present in an amount of about 30 wt % to about 99wt %, and preferably about 40 wt % to about 60 wt %, based on the totalweight of the coating composition.

The silicone resin useful for the present invention is not particularlylimited and can be that well known to persons skilled in the art, thatis, an organic polysiloxane resin with a main chain consisting ofrepeating Si—O bonds where hydrogen atoms or organic radicals aredirectly bonded to the silicon atoms, and of the formula[R_(n)SiO_(4-n/2)]_(m), wherein R represents hydrogen or an organicradical, and independently is hydrogen, C₁₋₆ alkyl, C₂₋₅ epoxy, or C₆₋₁₄aryl, and preferably is hydrogen, methyl, ethyl,

or phenyl; n is the number of the hydrogen atom(s) or organic radical(s)bonded to the silicon atom and is in the range from 0 to 3; and mrepresents the degree of polymerization, and is an integer of 2 or more.The steps for constructing the chemical structure of polysiloxaneinclude determining the length of the polymeric chain, branching, andlocating the places for attaching hydrogen(s) or organic group(s). Inview of the chemical structure, letters M (denoting monofunctionalgroup), D (difunctional group), T (trifunctional group), and Q(tetrafunctional group) can be used to represent the structural group(s)introduced into the polymeric molecule.

Examples of Commercially available silicone resins include, but are notlimited to KBM-1003, KBE-402, KBE-403, KBM-502, KBM-04, KBE-13, andKBE-103 manufactured by Shin Etsu Company; and Z-6018 and 3037manufactured by Dow Corning Company.

The silicone resins can be used in single species and in combination oftwo or more species. The silicone resin useful for the present inventioncan be an oligomer of the formula R¹O—[SiR₂O]_(w)—SiR₂(OR¹) in which wis an integer of 1 to 1000, R is as defined hereinbefore and R¹ isindependently H, C₁₋₃ alkyl or C₂₋₅ epoxy and preferably is methyl,ethyl, or

Such oligomer imparts the inventive coating composition with betterfilm-forming property, dispersivity, and ductility, and a high surfacehardness after being cured.

The suitable preparation method for the silicone resin used in thepresent invention is not particularly limited. According to thepreferred embodiment of the present invention, the silicone resin isformed through a sol-gel process. The sol-gel process includessuspending a raw material of solid particles of about several hundrednanometers in size (generally, an inorganic metal salt), in a liquid. Ina typical sol-gel process, the reactant will undergo a series ofhydrolysis and polymerization reactions, to generate a colloidalsuspension, in which the resulting substance in the colloidal suspensioncondenses into a new phase of a solid polymer containing solution, thatis, gel. The properties of the prepared sol-gel depends on the speciesof the raw material, the species and concentration of the catalyst, thepH value, the temperature, the amount of the solvent, and the speciesand concentrations of the alcohol and the salt.

The coating composition of the present invention may optionally comprisenano-size inorganic particulates, such that the surface of thephotocatalyst composite is covered with a layer of the inorganicparticulates, so as to avoid direct contact of the photocatalyst withthe substrate when the coating composition is coated onto the surface ofthe substrate, and to avoid the deterioration of the substrate that canbe easily caused due to the oxidation property of the photocatalyst. Ifpresent, the amount of the inorganic particulates is about 0.1 wt % toabout 40 wt %, based on the total weight of the composite material. Theinorganic particulates useful for the present invention are notparticularly limited, and generally may be selected from silica (SiO₂),alumina (Al₂O₃), cadmium sulfide (CdS), zirconia (ZrO₂), calciumphosphate (Ca₃(PO₄)₂), calcium oxide (CaO), and a combination thereof,with SiO₂ being preferred. According to a preferred embodiment of thepresent invention, the photocatalyst composite is coated with a layer ofporous inorganic particulates. Specifically, the photocatalyst compositein the composite material of the present invention is coated with alayer of porous inorganic particulates, and thus will not directlycontact and destroy the substrate, and external impurities (for example,odor molecules and bacteria) can penetrate the porous inorganicparticles through diffusion, arrive at and be absorbed on thephotocatalyst material, and are photocatalytically decomposed, therebyachieving the cleaning, antimicrobial and deodorization purposes.

An organic solvent may be further added to the coating composition ofthe present invention, depending on the requirements in application.When the organic solvent is used in the coating composition of thepresent invention, the amount is about 1 wt % to about 95 wt %, andpreferably about 65 wt % to about 90 wt %, based on the total weight ofthe coating composition. The organic solvent may be any of those wellknown to persons skilled in the art, and may be, for example, but is notlimited to, an alkane, an aromatic hydrocarbon, an ester, a ketone, analcohol, or an ether alcohol. The alkane solvent useful in the presentinvention may be selected from the group consisting of n-hexane,n-heptane, iso-heptane, and a mixture thereof. The aromatic hydrocarbonsolvent useful in the present invention may be selected from the groupconsisting of benzene, toluene, and xylene, and a mixture thereof. Theketone solvent useful in the present invention may be selected from thegroup consisting of methyl ethyl ketone (MEK), acetone, methyl iso-butylketone, cyclohexanone, and 4-hydroxy-4-methyl-2-pentanone, and a mixturethereof. The ester solvent useful in the present invention may beselected from the group consisting of iso-butyl acetate (IBAC), ethylacetate (EAC), butyl acetate (BAC), ethyl formate, methyl acetate,ethoxyethyl acetate, ethoxypropyl acetate, ethyl iso-butyrate, propyleneglycol monomethyl ether acetate, and pentyl acetate, and a mixturethereof. The alcohol solvent useful in the present invention may beselected from the group consisting of ethanol, iso-propanol, n-butanol,and iso-pentanol, and a mixture thereof. The ether alcohol solventuseful in the present invention may be selected from the groupconsisting of ethylene glycol monobutyl ether (BCS), ethylene glycolmonoethyl ether acetate (CAC), ethylene glycol monoethyl ether (ECS),propylene glycol monomethyl ether, propylene glycol monomethyl etheracetate (PMA), and propylene glycol monomethyl propionate (PMP), and amixture thereof.

The present invention further provides an energy-saving material, whichcomprises a substrate and a film formed from the coating composition asdescribed above on at least one surface of the substrate. The coatingcomposition of the present invention can be applied onto the at leastone surface of the substrate by a common application method, which isfor example, coating, spraying, or dipping, and then dried to form asmooth film. The existing energy-saving materials generally have thedisadvantages of low coating hardness and being likely to be scratched,such that the coating is very likely to be scratched after a long periodof time, and the scratched coating in turn seriously influences theaesthetic appearance of an article, such as window. According to apreferred embodiment of the present invention, the film of theenergy-saving material has a pencil hardness of H or higher andpreferably 3H or higher, as measured according to JIS K5400 standardmethod, and can effectively overcome the above-mentioned disadvantages.

The above-mentioned substrate includes, but is not limited to, glass,plastic, heat insulation plate for buildings, metal, ceramic tile, wood,leather, stone, concrete, mural, fiber, cotton fabric, appliances,lighting devices, and computer casings, with glass and heat insulationplate for buildings being preferred.

According to a specific embodiment of the present invention, theenergy-saving material includes a glass and a film formed by applyingthe foregoing coating composition by coating, spraying, or dipping on atleast one surface of the glass. The film has a thickness of about 0.5 toabout 50 micrometers. The energy-saving material according to thepresent invention has a transmittance of the visible light underwavelength of 550 nm of about 70% or more, preferably of about 90% ormore. The energy-saving material of the present invention has a goodvisual effect and an infrared light (thermal radiation) reflectance ofabout 70% or higher, and exhibits a good heat insulation effect, so itcan substantially decrease the indoor temperature and reduce powerconsumption, has a better energy-saving effect and a highertransmittance of visible light, compared with a glass attached with atraditional heat insulation film available in the market, and thushaving the advantages of greatly reduced cost, simple application, andwide application in glass curtain for buildings or automobile glass.Furthermore, almost all the heat insulation materials (such as lanthanumhexaboride) contained in the coating compositions for energy-savingmaterials available in the market absorb, rather than reflect, theinfrared light in sunlight, and the absorbed infrared light is convertedinto heat energy, and stored in glass, such that the surface temperatureof the glass rises, and thus the risk of glass cracking exists.

Moreover, the photocatalyst composite in the coating composition of thepresent invention has superhydrophilic property, such that the moisturein the air is attracted to form a super thin aqueous film between thefouling and the photocatalyst composite and to reduce the adhesion ofthe fouling. In addition, the photocatalyst can also oxidize organicfouling particles and break down the structure thereof, such that theparticles will not be attached on the surface of the glass. Uponrainfall, due to the effect of superhydrophilic property, the rain waterevenly penetrates to an interface between the fouling and thephotocatalyst, and the fouling on the aqueous film can be easily washedoff when the rain water is accumulated to a sufficient extent, such thatthe frequency of maintaining the surface of a common glass clean withthe aid of human power is lowered, and the self-cleaning effect isachieved.

In the past, for obtaining energy-saving materials, treatments forshielding infrared light and absorbing UV light needed to be performedon the substrate, so effects both on shielding infrared light andabsorbing UV light can be achieved only after a multi-layer processingwas conducted on the substrate. However, by using the coatingcomposition of the present invention, an energy-saving material havingthe effects on shielding infrared light and absorbing UV light can beobtained only through one time application treatment on the surface ofthe substrate. As the film applied on the substrate containsphotocatalyst material, it can absorb UV light, thus providingself-cleaning, anti-fog, antimicrobial, and deodorization efficacies;and due to the presence of the heat insulation material, the film canalso effectively reflect infrared light so as to reduce thetransmittance of the infrared light while allowing the visible light topass through. In addition, since the size of the particles contained inthe film is less than the wavelengths of the visible light, theparticles will not scatter the transmitted light and will not influencethe quality of the transmitted light, and the transparency of thesubstrate can be maintained.

The present invention further provides a method for preparing a coatingcomposition, which includes obtaining an intermediate product oftitanium sulfate through hydrolysis of titanium tetrachloride, thenadding a heat insulation material, to obtain a photocatalyst compositepowder at a low temperature, and then mixing and grinding the resultingphotocatalyst composite powder and a silicone resin, to obtain thecoating composition of the present invention.

According to a preferred specific embodiment of the present invention, asol-gel silicone resin and a photocatalyst composite powder in suitableproportions are mixed and optionally a solvent is added, followed bygrinding, so as to obtain the coating composition of the presentinvention. The above-mentioned photocatalyst composite powder can beobtained by the process comprising the following steps:

(a) obtaining a white gel hydrate through hydrolysis of titaniumtetrachloride;

(b) adding concentrated sulfuric acid into the resulting hydrate in areactor, and stirring for 10-50 min, to obtain a titanium sulfatesolution;

(c) sufficiently mixing the titanium sulfate solution, and stirring for0.5-5 hrs at normal temperature;

(d) heating to 80-100° C., and reacting for 2-7 hrs at a constanttemperature; and

(e) adding an ITO powder at a suitable ratio, stirring for 1-4 hrs formixing, dripping 4-6 M aqueous sodium hydroxide solution, filtering,washing, and drying at room temperature, to obtain the photocatalystcomposite powder (TiO₂+ITO).

The present invention will be further described in detail through thefollowing examples. It should be understood that the examples are merelyused to exemplify the present invention, but not intended to limit thescope of the present invention. Any modification or alteration obviousto persons skilled in the art and made without departing from the spiritand principle of the present invention should fall within the scope ofthe present invention.

EXAMPLES

In the examples and comparative examples below, the percentages areweight percents (wt %), unless otherwise stated.

Example 1

200 ml of a 3.9 M titanium tetrachloride solution was diluted with waterto a total volume of 2000 ml, and then 500 ml (5 M) of aqueous ammoniawas dripped, to generate a white titanium hydroxide precipitate, whichwas filtered, washed with deionizer water (200 ml×3) to remove theremaining water, to obtain titanium hydroxide [Ti(OH)₄] as a white gel.

100-150 g of concentrated sulfuric acid (18M) was added to 250 g of theabove-mentioned titanium hydroxide, and stirred for 30 min, to obtain atransparent and clear titanium sulfate solution. The titanium sulfatesolution was placed in a reactor, 32.2 g of an aqueous SiO₂ solution(20%) was added, stirred for 4 hrs at normal temperature, then heated to100° C., and reacted for 2 hrs. 100 g of an aqueous ITO solution (10%)was added, the reaction was stirred at normal temperature for 2 hrs, toobtain a mixture.

600 ml (5 M) of an aqueous sodium hydroxide solution was dripped, thenthe resulting solution was adjusted to a neutral pH, and a resultingprecipitate was filtered, washed, and dried at room temperature, toobtain a grey blue powder, which was detected through XRD to be aphotocatalyst composite of an anatase type photocatalyst and ITO.

The resulting photocatalyst composite was added to a silicone resin(having a solid content of 27%) at a ratio (in weight) of thephotocatalyst composite:resin=1:3, stirred, ground, dispersed, andapplied onto a glass plate to form a coating having a thickness of 5micrometers. A light transmittance measurement, organic (methylene blue)decomposition test, hydrophilic property test, and heat insulation testwere conducted.

A blank glass plate and a coating were placed in a UV/visible/nearinfrared spectrometer (manufactured by JASCO Incorporation, Model V-570)respectively, to measure the light transmittance in the range of UVlight to near infrared light. The test results are as shown in FIG. 1(in which the range between the two vertical lines represent visiblelight). The zigzag line represents the transmittance values of anuncoated glass plate (the transmittance is about 100%), the solid linerepresents the transmittance values of a glass plate with a singlecoating on one surface, and the dot line represents the transmittancevalues of glass plate with coatings on both surfaces. It can be seenfrom the test results that, the coating of the present invention cangreatly reduce the transmittance of UV light and near infrared light,and effectively shield UV light and near infrared light.

(35±0.3) ml of methylene blue was added to a cylindrical test columnhaving an inner diameter of 40 mm and a height of 30 mm, and then squareglass with a side length of (6012) mm and having a coating was placedthereon. The coating was irradiated with UV light of (1.00±0.05) mW/cm²for 6 hrs in total, and the decomposition rate of methylene blue wasmeasured every 1 hr. The test results are as shown in FIG. 2. It can beseen from the test results that, upon irradiation with UV light, thecoating of the present invention can effectively decompose organics(methylene blue), and thus has photocatalytic property.

Taking a square glass having a side length of (100±2) mm with a coatingas a test plate, 1 μL of water contacted with the test plate, an imageis captured, and the contact angle was measured with a contact angletester. The coating was irradiated with UV light of (1.0±0.1) mW/cm²,and the contact angle was measured once every 50 hrs. The test resultsare as shown in FIG. 3. It can be seen from the test results that, thecoating of the present invention has superhydrophilic property uponirradiation with UV light.

A coating was placed at a position of about 20 cm below an infraredlight bulb (PHILIPS Corporation), and a beaker containing 100 g of waterwas placed at a position of about 15 cm below the glass coating, andirradiated with the infrared light bulb, and the surface temperature wasregularly measured with an infrared thermometer (TES series, TESElectrical Electronic Corp.) every 5 min. The test results are as shownin Table 1 below, and the surface temperature of the coating after30-minutes of irradiation is as shown in Table 2 below.

Example 2

200 ml of a 3.9 M titanium tetrachloride solution was diluted with waterto a total volume of 2000 ml, and then 500 ml (5 M) of aqueous ammoniawas dripped, to generate a white titanium hydroxide precipitate, whichwas filtered, washed with deionized water (200 ml×3) to remove theremaining water, to obtain titanium hydroxide [Ti(OH)₄] as a white gel.

100-150 g of concentrated sulfuric acid (18M) was added to 250 g of theabove-mentioned titanium hydroxide, and stirred for 30 min, to obtain atransparent and clear titanium sulfate solution. The titanium sulfatesolution was placed in a reactor, 32.2 g of an aqueous SiO₂ solution(20%) was added, stirred for 4 hrs at normal temperature, then heated to100° C., and reacted for 2 hrs. 100 g of an aqueous ATO solution (15%)was added, the reaction was stirred at normal temperature for 2 hrs, toobtain a mixture.

600 ml (5 M) of an aqueous sodium hydroxide solution was dripped, thenthe resulting solution was adjusted to a neutral pH, and a resultingprecipitate was filtered, washed, and dried at room temperature, toobtain a deep blue powder, which was detected through XRD to be aphotocatalyst composite of an anatase type photocatalyst and ATO.

The resulting photocatalyst composite was added to a silicone resin(having a solid content of 27%) at a ratio (in weight) of thephotocatalyst composite:resin=1:3, stirred, ground, dispersed, andapplied onto a glass plate to form a coating having a thickness of 5micrometers. A heat insulation test was conducted.

A coating was placed at a position of about 20 cm below an infraredlight bulb (PHILIPS Corporation), and a beaker containing 100 g of waterwas placed at a position of about 15 cm below the glass coating, andirradiated with the infrared light bulb, and the surface temperature wasregularly measured with an infrared thermometer (TES series, TESElectrical Electronic Corp.) every 5 min. The test results are as shownin Table 1 below, and the surface temperature of the coating after30-minutes of irradiation is as shown in Table 2 below.

Comparative Example 1

200 ml of a 3.9 M titanium tetrachloride solution was diluted with waterto a total volume of 2000 ml, and then 500 ml (5 M) of aqueous ammoniawas dripped, to generate a white titanium hydroxide precipitate, whichwas filtered, washed with deionized water (200 ml×3) to remove theremaining water, to obtain titanium hydroxide [Ti(OH)₄] as a white gel.

100-150 g of concentrated sulfuric acid (18M) was added to 250 g of theabove-mentioned titanium hydroxide, and stirred for 30 min, to obtain atransparent and clear titanium sulfate solution. The titanium sulfatesolution was placed in a reactor, 32.2 g of an aqueous SiO₂ solution(20%) was added, stirred for 4 hrs at normal temperature, then heated to100° C., and reacted for 2 hrs. 100 g of an aqueous lanthanum hexaboridesolution (10%) was added, the reaction was stirred at normal temperaturefor 1 hr, to obtain a mixture.

600 ml (5 M) of an aqueous sodium hydroxide solution was dripped, and aresulting precipitate was filtered, washed, and dried at roomtemperature, to obtain a gray blue powder, which was detected throughXRD to be a photocatalyst composite of an anatase type photocatalyst andlanthanum hexaboride.

The resulting photocatalyst composite was added to a silicone resin(having a solid content of 27%) at a ratio (in weight) of thephotocatalyst composite:resin=1:3, stirred, dispersed, and applied ontoa glass plate to form a coating having a thickness of 5 micrometers. Aheat insulation test (utilizing an infrared light bulb, PHILIPSCorporation) was conducted.

A coating was placed at a position of about 20 cm below an infraredlight bulb, and a beaker containing 100 g of water was placed at aposition of about 15 cm below the glass coating, and irradiated with theinfrared light bulb, and the surface temperature was regularly measuredwith an infrared thermometer (TES series, TES Electrical ElectronicCorp.) every 5 min. The test results are as shown in Table 1 below, andthe surface temperature of the coating after 30-minutes of irradiationis as shown in Table 2 below.

Comparative Example 2

A commercially available heat insulation paper (manufactured by TopColor Film Co. Ltd., trade name; SD series Top Colour) was attached to aglass surface, and placed at a position of about 20 cm below an infraredlight bulb, and a beaker containing 100 g of water was placed at aposition of about 15 cm below the glass attachment and irradiated withthe infrared light bulb, and the surface temperature was regularlymeasured with an infrared thermometer (TES series, TES ElectricalElectronic Corp.) every 5 min. The test results are as shown in Table 1below, and the surface temperature of the attachment after 30 minutes ofirradiation is as shown in Table 2 below.

TABLE 1 Temperature test Temperature (° C.) Comparative Comparative Time(min) Glass Example 1 Example 2 Example 1 Example 2 0 24 24 24 24 24 534 34 33.8 34 34.8 10 39.8 35.3 34.7 38.3 39.3 15 42.6 39.8 38.5 40.140.9 20 45 42.3 39.8 43.1 44.1 25 46.1 43.6 42 45.8 44.8 30 48.6 43.6 4346.5 45.1

TABLE 2 Surface temperature of the glass after 30 minutes of irradiationTemperature (° C.) Comparative Comparative Time (min) Glass Example 1Example 2 Example 1 Example 2 30 70.8 60 61.4 86 68.4

It can be seen from the comparison of the results in Table 1 that,application of the coating having the coating composition of the presentinvention on the surface of the glass can effectively insulate heat.

It can be seen from the comparison between Examples 1 and 2 andComparative Example 1 that the coating composition of the presentinvention can effectively reflect infrared light, resulting in a lowersurface temperature on glass, thereby avoiding the risk of glasscracking.

It can be seen from the comparison between Examples and 2 andComparative Example 2 that the coating composition of the presentinvention, comparing to heat insulation paper, provides a lower surfacetemperature on glass coating. The coating composition can be appliedmore easily than heat insulation paper, and is less likely to accumulateheat energy or generate heat convection, thereby providing a better heatinsulation effect.

1. A coating composition, comprising a photocatalyst composite and a silicone resin, wherein the content of the photocatalyst composite is about 1 to 70 wt %, based on the total weight of the composition, and the photocatalyst composite comprises: (1) a heat insulation material selected from the group consisting of antimony tin oxide (ATO), indium tin oxide (ITO), aluminum zinc oxide (AZO), indium zinc oxide (IZO), and gallium zinc oxide (GZO), and a combination thereof; and (2) a photocatalyst material selected from the group consisting of titanium dioxide, zinc oxide, strontium titanate, and tin oxide, and a combination thereof, wherein the content of the photocatalyst material is about 10 to 90 wt %, based on the total weight of the photocatalyst composite.
 2. The coating composition according to claim 1, wherein the silicone resin is prepared through a sol-gel process.
 3. The coating composition according to claim 1, further comprising an organic solvent.
 4. The coating composition according to claim 1, wherein the heat insulation material is ATO or ITO.
 5. The coating composition according to claim 1, wherein the content of the photocatalyst material is about 40 to 85 wt %, based on the total weight of the photocatalyst composite.
 6. The coating composition according to claim 1, wherein the photocatalyst material is titanium dioxide.
 7. The coating composition according to claim 1, wherein the photocatalyst composite has a particle size of about 2 to 100 nanometers (nm).
 8. The coating composition according to claim 1, further comprising inorganic particulates selected from the group consisting of silica (SiO₂), alumina (Al₂O₃), cadmium sulfide (CdS), zirconia (ZrO₂), calcium phosphate (Ca₃(PO₄)₂), and calcium oxide (CaO), and a mixture thereof.
 9. An energy-saving material, comprising: a substrate; and a film formed from the coating composition according to claim 1 on at least one surface of the substrate.
 10. The energy-saving material according to claim 9, wherein the film is formed by coating, spraying, or dipping the coating composition according to claim 1 on at least one surface of the substrate.
 11. The energy-saving material according to claim 9, wherein the film has a pencil hardness of H or higher as measured according to JIS K5400 standard method. 